I just got my 165 swap drivable. The 3rd or 4th boosted pull on the back road behind my work and #2 rod decided to part ways with the small end/piston. The engine was stock. The only upgrade was a set of ARP head studs. And boost was at wastegate pressure.

The rod itself snapped in half. The bearings are fine and I had oil pressure. The broken rod destroyed the oil pan and the bottom of the block.

So...looks like I'll be getting another motor. I'll be building it up with stronger rods. My question is about the pistons...does anyone else have problems with the stock pistons? I was thinking of just upgrading the rods and leaving the stock pistons in there.

There have been some discussion on the rods being weaker than the previous gens. Crazy to see someone actually breaking one, how much boost were you pushing. If I were your and tearing it apart just replace both rods and pistons.

I've never heard of one failing at that boost/pwr level. There are numerous 300+ whp ones running around reliably, so something else might be up. I would add the pistons while you're in there. If budget is an issue, then I would add oe 3rd gen rods and aftermarket pistons. Just my $0.02

I suspect it might have been bent or flawed in some way before I even got the motor.

But as far as stock pistons go, I wanted to see if anyone has problems with them? I think my power goals are realistic. I'm looking for somewhere around 350 at the flywheel. Maybe a new motor with upgraded rods and the ATS sweet 16 set up.

I have a friend with a gen4 in an sw20, his only mods are a t3t4 kit and water meth injection. He ran for 3 years at 17psi and just a couple of months ago lost a rod. I'm planning to go t3t4 as well since I like the way his car drove. I will be dropping mine out to do forged pistons on gen2 rods and head studs as well.

All that being said your failure seems like a fluke, but if I had plans to beat on it forged pistons on early rods and it should be damn near bullet proof at 400 whp

They are "weaker". But not at your power & boost levels. They bend with too much power/advance. Don't typically break.

I've been running a bone stock 4th gen (except ARPs) with a GT3071 @ 23psi since 2008. Drag race, road race, etc. Mostly on pump gas and at one point on a failing pump. I would not recommend it but I could show you dozens running a LOT of boost on stock 4th gens at 300+ whp.

I thought I'd update this. It took forever to get my upgrade parts and new engine. I know the 4th gen rod thing is a big controversial subject, so here is my experience. My new engine has been built up with Wiesco pistons and eagle rods with ARP hardware holding a lot of the engine together. I'm not risking another rod snapping, so I'm on the side of weak rods.

The rod could have been defective, or the engine could have been abused by a previous owner (I'm assuming you didn't get a brand new 4th gen crate motor somehow). Did you ever drive that motor before it went in your car?

Yes, I drove it for a bit. Don't know what caused it. Could have been defective. Who knows. It looked fine when I tore the engine down for a clean up and reseal. I checked all my bearings and sealed it up. Stuck it in the car and ran it for a couple weeks.